Impact of vitamin D deficiency on defective endometrial decidualization and the repressive role of VDR in the epigenomic network [CUT&Run]

The identification of the factors regulating female reproduction is critical to understanding how the environment and nutrition impact female fertility and reproductive health. Vitamin D and its cognate receptor, VDR, are recognized for their role in calcium homeostasis; however, their broader impact on female reproduction remains underexplored. Here, we demonstrate that vitamin D and VDR are involved in the hormonal induction of uterine stromal cell differentiation, known as decidualization. Mice fed a vitamin D-deficient diet displayed an impaired hormonally induced decidual response. In a human endometrial stromal cell line, T-HESC, VDR decreases during decidualization. siRNA knockdown of VDR in T-HESC enhanced decidualization, while overexpression of VDR inhibited decidualization. Chromatin accessibility and histone modification analyses revealed that VDR functions as a chromatin regulator, restricting accessibility and maintaining transcriptional repression in specific genomic regions. Transcriptomic analyses confirmed that VDR broadly modulates gene expression, with most ligand-mediated effects dependent on its presence. These findings identify VDR as a key regulator of transcriptional and chromatin landscapes in endometrial stromal cells, offering novel insights into vitamin D signaling in reproduction. This study highlights the potential of targeting vitamin D pathways to treat uterine disorders associated with impaired decidualization.